Control system



H. D. JAMES.

CONTROL SYSTEM.

APPLICATION FILED MAY 12,'1919.

Pwaentefi Jam. 11, 19210 WITNESSES:

UNITED STATES PATENT OFFICE.

HENRY D. JAMES, OF EDGEWOOD PARK, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELEGTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYL- VANIA.

CONTROL SYSTEM.

Specification of Letters Patent. Patent d J 3 11 1921:

Application filed May 12, 1919. Serial No. 296,491.

To all whom it may concern:

Be it known that I, HENRY D. JAMES, a citizen of the United States, and a resident of Edgewood Park, in the county of All'e gheny and State of Pennsylvania, have invented a new and useful Improvement in Control Systems, of which the following is a specification.

My invention relates to motor-control systems and particularly to systems for controlling the. excitation, during acceleration, of the shunt field-magnet windings of directcurrent motors.

The object of my invention is to provide an improved control system of the abovedesignated character.

In a system arranged according to my invention, the resistor that is in circuit with the shunt field-magnet winding is controlled by a normally-open switch that is provided with a coil connected across the armature resistor. Upon the current falling to a predetermined value, or upon the armature re- A direct current motor, having an armature 1 and a shunt field-magnet winding 2,1s

connected between line conductors 3 and 4 by a line contactor 5, with an accelerating resistor 6 in series with the armature 1. The

contactor 5 is adapted to be closed, upon a master switch 7 being moved to its first position, to establish the circuit of an actuating "coil 8, which circuit comprises contact members 9 and 9 A plurality of contactors 10, 11 and 12 are adapted to effect the short-circuiting ofresistor portions 13, 14 and 15, respectively, of the resistor 6, upon the master switch 7 being successively actuated to positions in which it engages contact members 16, 17 and 18,- respectively.- The contactors 10, 11 and 12 are respectively provided with actuating coils 19, 20 and 21, the circuits of which are respectively controlled by the contact members 16, 17 and 18.

.I have shown the contactors 5, 10, 11 and 12 as controlled by a master switch 7 of the drum t pe, but it will be understood that a control er of any other type may be substi- 2, the effective portion of which may be ad justed as desired and the remaining portion of which is under the control of a relay 23, having an actuating coil 24 that is connected across portions of the resistor ,6, as, for example, the portions 14 and 15. In Fig. 2, the resistor 22 is adapted to be controlled in two steps by relays 23 and 25 having actuating coils 24 and 26, respectively, which are connected across portions of the resistor 6' as, for example, the portions 13 and 14, and 14 and 15, respectively. It will be understood that the particular connecting points of the coils 24 and 26 which are, here shown are shown for purposes of illustrationonly' and that it is within the scope of my invention to connect these coils in relation other than that above described. a

The operation of the system of Fig. 1 may be described as follows: Upon the actuation of the master switch 7 to its first position, wherein it engages contact members 9 and 9, a circuit is established from the line conductor 3, through the contact members 9 and 9, which are bridged by the master switch 7, and the coil 8, to the line conductor 4. The contactor 5 is thereupon closed by its actuating coil 8 to close the motor circuit. Current then flows from the line conductor 3, through the armature 1 and the resistor 6 on the one hand and the shunt field-magnet winding 2 and the resistor 22 on the other, in parallel, and the contactor 5, to the line conductor 4. The

coil 24 becomes thereupon energized by the voltage drop across that portion of the resistor to which it is connected, effecting the closing of the relay 23 and the short-circuiting of the resistor 22. be then accelerated, with the field-magnet winding 2 strongly excited.

Further actuation of the master switch 7 to its successive positions will result in the successive closin of the circuits of the coils 19, 20 and 21, w ich, in turn, effect the successive closing of the contactors 10, 11 and 12 to short-circuit the resistor portions 13, 14 and 15. Upon the resistor portions 14 and 15 becoming short-circuited, the coil 24 be tion 16 of theresistor 6 whic when the motor speed attains a predetermined value, is so small" that the coil 24, energized in accordance therewith, is not able to maintain subjected to voltage drop of a porthe relay 23 closed. The relay 23 is therefore opened by force of avity to efiect the i reinserting into the circuit of the field-magnet winding-2 of the resistor 22, whereupon the motor accelerates to its maximum s d. The system of Fig. 2 is similar to that of Fig.1, the coil 24 becoming deenergized of the resistor 22 is inserted into the circuit 2. When the recoil 26 is unable to maintain the relay 26 closed, whereupon the remainin portion of the resistor 22 is inserted into t e circuit of the field-magnet windin 2.

In this system, th'reiays 23 and 25 may 0 en alternately with the closin of some of t e contactors 10, 11 and-12. Thus, in the system as illustrated, the relay 23 'is opened following the closing of the contactor 11 and before the closing of the'contactor 12a,

The system may be so desi ed, however, that the relay 23 opens followmg the closing of the contactor 10. Thus, the resistor. port1on..14 maybe so designed that after the motor has attained a certain predetermined speed the voltage drop across the resistor 14 will be suflic1ent to energize the coil 24 strongly enough 'to maintam the relay 23 close Although I haveshown twos'ystems embodymg my invention, it will be understood that the invention is not restricted thereto, but that other and equivalent systems may be devlsed falling within the spirit and scope of the invention, as expressed n the appended claims.

I claim as my invention:

1. The combination with an electric motor having armature and field-magnet windings and resistors in circuit therewith, of means controlled in accordance with the drop, in potential across one of said resistors for controlli the other of said resistors.

2.- The combination with an electric motor having armature and shunt field-magnet windings and resistors in circuit therewith, of means controlled in accordance with the drop in potential across said armature rcsistor for controlling said field-magnet resistor.

3. The combination with an electric motor having armature and shunt field-magnet windin and resistors in circuit therewith, of a switch for controllin said field-magnet resistor having a control mg coil connectd across said armature resistor.

4. The combination with an electric motor having armature and shunt field-ma not windin resistors in circuit therewit l, a switch i short-circuiting said armature rcsistor, and means for actuating said switch, of a switch biased to openlposition for short circuiting said armature resistor when closed and having. a closing coil connected across said armature resistor that is adapted to ermit the closin of said biased switch folibwin the actuatlon of said actuatin means.

5. he combination. with an electnc motor having armature and shunt field-magnet windin and resist rs in series therewith, of a pfdrality of s itches for controlling subscribed my name this 23d day of April,

across portions of said armature re- HENRY D. AMES.

said field resistor having actuating coils con- 

